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Flip-Chip Packaging Using P ES (Printing Encapsulation Systems)and PES Underfill Epoxy Resin

Atsush i OkunoN o r i t a k a O y a r n a , K o i c h i r o u N a g a i , a n d T s u n e k a z uHash = i o to

J A P A N R E C CO-,LTD-5 - 1 , - C ~ i o m e , D o u ~ h o , T a k a t s u k i - - ~ 1 t y , O s a k a , J A P A N ,

TEL- 8 1 - 7 2 6 - 6 9 - 5 2 3 1F A X - 8 1 - 7 2 6 - 6 9 - 5 2 3 0

A B S T R A C TIn recentry,flip-chip technology have been very rapidly

progressing at this stage of laboratory. But industry ottli-chip don t progress with sati sfac tory . Because it spackaging m at er id s ar e using low viscosity Liquid typeundertill epoxy resin, and pdckaging methods are usingdispenser systems. These systems have many problems tomass production as hllows.

( 1 ) This process needs many times to underfill epoxyresin tor flip-c hip.

( 2 ) This epoxy resin must u w low viscositv epoxy resint o undertill under LSI, an d i t ca n t contain muchtiller. It is difficult tG get low expansion epoxvresin system. It occures delamindtion between L S Idrld underfi l l epoxy resin at sometimes.

W e soloved these problems using our P E > process and PESepoxy resin.

At the first step, we developed new type underli l lepoxy re5in. This epoxy resins have low expansion, highpurity, high adhesive strengh, high Tg, high humidityresistanLe dnd high electric resistdnc e. This iindert il lepoxy rc5in didn ' t occured m i s s m a t i hirig between L \Iandboard.

At the secondary step, we developed the s p w i a l PE5 fo runderfill method ot f l ip-chip. W e can ge t no bubbleprocess tor underfill pachdging 01 flip-c hip. Thisprocess is tormed of flip-chip bumping --PES printing +Vacuum procebs +h eat curing i t es t . This process is verysimple and undertill many LS1 at once t ime. W e can ge tno bubble Ilip-chip packaging and get high reliabilitytllp-chip packdging.

INTRODUCTIONQith t he advance o f small size, light weight, and high

funct ion ot Flec t ronics in the tu ture , MCM will spreddrdpidly. Three met hods ot mounting technology of LS Ichips for MCM a r e as follows;

1 ) Wire bonding method(W8)This method is using wire and bond with LS1 chipand subs trat e using this wire. This need dround ofLS1 chip for wire bonding area.

2) T A B methodThis method is forming bump on e lec t rode of L S Ichip and bonding t o film ledd. TAB can connec t a ta time with many pin count and narrow pitch. Butthis need extensive area of mounting dnd price isexpeni i v e for using poiyimide film.

3 ) Flip-chip methodThis method is bonding with Circuit board usingfacedown of LS I chip. This method is possible toconne ct with th e most hiah density using only LS1chip a rea .

The former packaging method o f TAB, and WH are usmgTransfer molding method and dis pms er method. Buttransfer molding method rnust use high expensive rnetdldie. and M C M having mdny model changing is no t su i tab lefor this method. Dispenser method need much pottingtimes and thickness of packaging is not uniform. Thrsdon t tit tor large volume production.

W e succeed i n PES(Printing Encdpsuhtion Systems)dekelopments ' h ) . PES can solve the above-statedproblems at one t ime. PES hdve alreddy many applicationresults of COB and TAB.

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R e s i n S u p p l i e rA ' t f e r C u - e L o n e p r e C u r e z o n eackaging rnethod of flip-chip 15 using the formerdispensing method. This flows low viscosity epoxy resin \ /-- 77around LS1 with di>penser and till-up this epoxy resinat atmosphere. l inti l now, sizs o f IC dre small and gapbetween IC and circuit board is more than i0 0u , and we nc-an underl ill t o this gap. V n - L o a a r n g C u r ! n a O v e n lair Chamber Screen Printer Loa ding

But this method t akes long time t o fill epoxy resin Fig.l. PES Processunder LSI. It is difficult to underfill epoxy resin inmany LS1 a t a time. This don't fit large volumeproductions. 'This must till a t atmo spher e and use lowviscosity epoxy resin only. For it, this cause rniss-rnacthing of exparision between LSI, low viscosity epoxyresin and substrate and generate delanrinations if LSIfrom now use. This method have many problems forreliability of LSI.

W e developed low expansion epoxy resin, an d used ourPES. W e c o u l d sucess no delamination and large volumeproduction process tor flip-chip of LSI. W e repor teepoxy resin and PES technology in this paper.

E X P E R I M E N T

Fig.2. Dispenser Process

Table 2 . Reliability Test

Tes t Tes t Parameter sPCT 121 Zatm, 1 0 0 % R H , 2 0 0 h r .High Tem.,Storage. 150t, 1,000hrsW e prepared five underfill epoxy resins having Humidity Test 85C,t '85%RHdifferent viscosity, and expansion for flip-chip. These Thermal cycles -55T t o + 150t, 500cyles

original rpoxy resins dre using tor COB applications Popcorn Testand have high reliability for LSI. On this t ime, wemoditied thes e epoxy resin t o flip-chip applications.

85"clX5%/168hrs+ZZ5~Re f l o w

Properties of these epoxy resins show Table 1 .W e used sham elements having 0.5 gape between LS l an d R E S U L T and C O N C L U S I O N

circuit substrate. Materidl substrate IS BT substrate.Methods ot underfill used two types. One rnrthod is N o Boide Process

PES, and other method IS dispenser. W e compered withPE5 and dispenser. Fig.1 shows P F 5 process, and Fig.2shows d spenser.

W e performed therma l cycling, PCT, popcon testing,high teriiperature ztrordge and humidity test, hymiditytest and storage a t high temperatur to r reliabilitytesr . These tes ts show Table 2.

I 11 11 1v \i -I3lac I 101'1.9 1.5 1.0 0.6 0.3

3 .5 2.1 2.5 1.5 0.9

Dispenser method draw slowly epoxy rewi around LSIwith needle, and ti11 e po xy r e ~ i n n de r LS I using acapillary action. But this method can f i l l epoxq resinunder L 5I when it use low viscosity resin. But it itu s e high v i s cos i t y epoxy resin, it 14 di fhcul t to tillup epoxy resin under L51 with no voide. It I> dift icultto f i l l up resin with more than one thousand polse ofviscosity. This shows to l a b l e 3.

PES method can underfill high vis(ositv epoxy resine a s i l y with Fig.1 process. A s PES use Printinn-*Vacume-Cure process, no voide pdckaginf: can produce. N o

voide is very impor tant t o get hiRh reliability offlipchip packaging. Especially aiter reflow process.

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Table 3. Voide of Underfill Resin af ter Dispenser andPES. High Vo lu rne P rodu c t io n~ __ ~ _ _ _

Poss ib i l i t y o f lowexpansion epoxy r e s i n_____

Dispenser method is dilficult to underfill highviscosity epoxy resin as above. Low expansion epoxyresin contains l arge weight volume filler, andviscosity taking increasing filler content increaserapidly. The limit of viscosity and expansion tounderfill epoxy resin are 1,000poise and 25ppm. It isditticult to dispense viscosity more than I ,000poise.

The other side, as P E \ use printing machine, and highviscosity epoxy resin than 1,000poise can print easilyon arround LSI. The limit of viscosity and expansion byPE5 on this time experiment are 3,000poise and Sppm.Expansion Sppm is near to LS1 and sustrate expansion.Miss matching of expansion between LS1, underfill

epoxy resin and substrate ar e small . Table 4 showsthes e relation. A fter l6Xhr at 8 5 C / S 5% humidity,popcorn test(230"C) shows Table 5. From this, P E 3method IS suitable t o high density VLS I an d MCM.

Table 4 . Relation of , Underfill Workabilityand V i s c o s i t yE p o x y R e s i n V i s c o s i t y ( P o i s e ) D i s p en s e r P E S0500II 7001,000 a1,300 9 1 .0V 2,000 X a

T a b l e 5 . Popcon Test af ter Ref low.

E p o x y R e s i n P o p c o n T e s tI 10 secU 15 secm 20 secN' 35 se c\ 63 sec

* T i m e to Popcon a t 225t a fte r 168hrs, 85C/85%

Dispenser method underfill one by o n e t o LSI, an d ISdrawing using needie around LSI. It tdke about manytimes and i t need underfill for 1 5 min.

But PES use printing method, arid can print many LSI a ta t ime. Printing t im e need about 2 ' isec a t 150 X 15Omrnsize. A l l packaging resin thickness ar e uniform. But ifyou use dispenser, thicknesb of packagtngs are dl1d f herent.As ou r PES use magazine to magazine, after printing,

vacuum? and curing process can us e magazine, andproduce large volume flip-chip packaging easily.

From now, MCM containing Clip-chip, TA R and wirebonding can use PES, and produce large volume.

Table 6 shows ditferent of dispenser and PE S method.

Table 6. Handling Time of Dispenser and PES.Dispenser PES

Handling Time 1 Smin./LSI 30sec./LSI* It is times When Five LSI Flip-chips on oneboard packaged using Dispenser or PES.

R e l i a b i l i t y o t P E S Methoda r i d I t ' s Epoxy R e s i n~ ~

Table 7 shows comparison of dispenser method and PESmethod. PES method get higher reliability thandispenser, because PE5 method can sele ct highviscosityand high filler content epoxy resin. Waterabsorptions of high fi l ler contents epoxy resin aresmall than the general flip-chip underfill epoxy resin.Popcorn test and thermal cycling can get good result .From this, PES hdve th e broad selection ot packagingepoxy resin.

Table i . R p l i a b i l i t y ol Undcrlill E p o x y R e s i n .Ep o x y reLin P,CT H u i n i d i t y Thermal C y c l e s1 3 20 0720 7 / 2 0

[I 0/20 0120 3 / 2 01 0120 0120 0120b 0120 0120 0120\ 0120 0120 0120_______* PCT: 12 " c , 1 00'%RH,2001-lrs.FIumidityTest: SSLC/S5%/ 100011rs.T h e r m a l Cycles: - 5 5 ' c to 1 SOC .

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CONCLUSIONW e tested comparison of reliability and large volume

production of flip-chip underfill epoxy resin when weuse dispenser method and PES method.

( I ) PES method can use low expansion and lo w waterabsorption epoxy resin than dispenser method.

(2) PES process can get no voide underfill packaging.( 3) PES is very suitable the large size prodcutions

than dispenser method.(4) It is possible very easily to produce large volume

of MC M packaging contain flip-chip and wirebonding a t a tim e if it use this PES an d lowexpansion epoxy resin.

R E F E R E N C E S[ I ] A.Okuno, New Pack agin g ot Chip on Board by

Unique Printing M eth od 4 1 th, ECTC,P.8 4 3-X47( I99 )[ 1 A.Okuno, I Printing Encapsulation SystemdPES) o f

Advanced Multichip Module & COB device 42th,ECTC, P. 18 - 786( 992)

[ 31 A.Okuno, IEEE Transcation on Comp onen ts, Hybrids,arid Manu fact urin g Tec hnology, Vol. I 5, No. I , P.7 3-/7 ( 1992)

14 ) A.Okuno, IJnique EpoxyResin and PrintingEncapsulation Systems(PE5) tor Advanced Multi ChipModule, TAB, COB, and Flip-chip IEPS, P.506-5 18,(1YY3)

[ ) A.Okuno, High Reliability M C M Packaging UsingLow Stress Liquid Type Epoxy Resin bv PrintingEncapsulation Systems(PE5) 44th, FCTC.P. 147- 15 ,( 1994)

[61 A.Okuno, The Internati onal Jour nal ofMi c roc irc uits & Electronic Packaging, V o l . 1 /,No.2.

P. 14 3 - 1 5 1 ( 1944)

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